1. Field of the Invention
This invention relates to a motor vehicle door lock such as a side door lock, a rear door lock, a rear hatch lock, or a hood lock and a process for controlling a motor vehicle door lock.
2. Description of the Related Art
A motor vehicle door lock with the aforementioned mentioned features is known from practice and includes an electric motor drive for an assigned actuating or locking element of the motor vehicle door lock and a sensor for acquiring the position, especially the rotary position of the drive or the assigned actuating element, and a control means which for positioning of the drive or the actuating element in a set position shuts off or short circuits the drive at a shut-off point which precedes the set position in time and position. The electric motor drive at the shut-off point has a certain energy of motion which leads to a considerable slowing down, therefore to further motion until the drive and thus the actuating element stop. Accurate positioning of the actuating element in the set position is however only possible if the actual slowing down is considered when the shutoff point is established. It has been found in practice that the slowing down depends on various influences such that the positioning accuracy is adversely affected thereby.
An object of the present invention is to provide a motor vehicle door lock with an electric motor positioning drive and a process for control thereof to obtain accurate positioning independent of production tolerances under various operating conditions.
The object is achieved so that the actual position of the drive and of the actuating element is acquired or determined in the shut-off state and that for deviations from the set position the shut-off point is corrected accordingly for future positioning. Thus, adaptation is easily enabled which leads to enhanced precision positioning in the set position. In particular, production tolerances can be automatically balanced by the aforementioned measure. Furthermore, very accurate positioning is enabled even under different operating conditions.
Preferably, at least one current operating characteristic, for example, a start-up characteristic of at least one of the drive and the assigned actuating element, is acquired or determined when the drive is actuated. The at least one operating characteristic is used to establish a shut-off point which precedes the set position in time and position. In particular, it has been recognized that the start-up behavior of the drive can also be used to draw conclusions about the braking behavior of the drive. Thus, without using an additional sensor, better or more accurate characterization of the operating behavior of the drive or its electric motor is possible.
In general, a plurality of different operating or start-up characteristics can be determined. In a preferred embodiment, it is provided that the voltage which is applied to the electric motor drive when the drive is actuated is acquired as a first start-up characteristic, at least if the drive variable. Additionally, at least one of an initial speed, acceleration of at least one of the drive and the assigned actuating element is acquired as a second start-up characteristic. It has been found that by using the start-up characteristics, the required time or the positional setting of the shut-off point in advance of the set position which is to be assumed in the shut-off state can be established or determined. This can be explained by the fact that from the two indicated start-up characteristics, the temperature of the drive, which has a major effect upon its braking and shut-off behavior, can be estimated or approximately determined by using these start-up characteristics. Accordingly, depending upon the estimated temperature or the two aforementioned start-up characteristics, the advanced positioning of the shut-off point which is necessary for accurate positioning can be ascertained. In addition, the temperature of the drive can also be directly acquired by means of an additional sensor as an important parameter for establishing the shut-off point.
Generally, the shut-off point is determined depending upon at least one operating parameter while the drive is engaged. In particular, a corresponding table or the corresponding performance data is used to determine the shut-off point based upon one operating parameter or on several current operating parameters. Accordingly pre-established deviations can be stored as a correction table or correction field so that then after establishing the current shut-off point by at least one of a correction table and a correction field based upon at least one current operating parameter, a correction value is determined in order to correct the shut-off point. In the aforementioned process, of course, interpolations are used if necessary. Additionally functional relationships, matrices or the like can be used in performing the process.
Accordingly, the present invention accomplishes feedback during control, however, there is no control which is undesirably time-consuming for positioning at least one of the drive and the actuating element in a set position, but only correction or adaptation of the control parameters for future positioning after establishing a deviation. Other details, features, objectives and advantages of this invention are detailed below using the drawings of one preferred embodiment.